【作者】 秦晓冰；

【导师】 高英俊；

【作者基本信息】 广西大学 ， 理论物理， 2008， 硕士

【摘要】 相场法作为材料微观组织演变的一种模拟方法已经被越来越广泛的应用到各种常见的微组织演化的模拟当中。它通过场变量简单明了地表征出任何一种复杂组织的几何形貌、可以在相同的物理和数学模型下模拟诸如:形核、长大和粗化等不同的现象。因此它是计算机模拟各种微组织演化的首选方法,例如模拟凝固以及枝晶形成、Ostwald熟化、失稳分解、有序-无序相转变、马氏体相变、晶粒长大等等。为此,本论文探讨了宏观和微观相场法在晶粒长大和合金沉淀相析出两种微观组织演化中的具体应用。首先,应用宏观相场方法采用多序参量唯象晶粒长大相场模型,对单相多晶材料中最基本的显微组织演化过程之一晶粒长大进行二维模拟,初步验证了相场方法的有效性,结果表明模型符合经典长大规律,晶粒尺寸分布是时间相关的,并可以由Weibull函数很好的描述。在此基础上探讨了势阱参数λ和能量梯度系数K_i的大小对晶粒长大和晶粒尺寸分布的影响,得到结论:λ值越大越会抑制晶粒生长,随着K_i的增大,晶粒生长加速,并且所形成的晶界也越厚。其次,应用微观相场法在原子层面上对合金有序-无序相转变进行仿真,以Al₃Li合金作为具体研究对象,对其δ′相析出过程进行简单研究,探讨了δ′相沉淀机制、得出其粗化行为随有序相长大而发生。更多还原

【Abstract】 Phase-field method, as a method of simulating material microstructure evolution, has been applied to all common microstructure evolution simulation. It can simply characterize the geometric shape of any complex organization also can simulate different microstructure evolution such as: nucleation growth and coarsening in the same physical and mathematical model. So phase-field method has been the preferred method for computer simulating material microstructure evolution, just like solidification and dendrite growth, Ostwald pirening, Spinodal decomposition, order-disorder phase transformation, Martensitic transformation, grain growth and so on. In this thesis, we study Macro-phase field and Micro-phase field in the field of grain growth and alloy precipitation precipitates microstructure evolution.First, the normal grain growth under the condition of single phase was simulated in 2D by means of the macro-phase field method. The effectiveness of the phase-field method was proved. The results show that the phase-field model accords with the classic model of growth, and grain size distribution which can well described by Weibull function is time-dependent. On this basis, we study grain size and grain size distribution which are affected by the value of the potential well parametersγand the energy gradient coefficient K_i. Conclusion: first, theγ-value greater inhibit grain growth, with the increase of K_i, grain growth accelerated, and by theformation of grain boundaries and the more thick. Second, the atomic-scale computer simulation of order-disorder phase transformation is conducted under the micro-phase field model. We choose Al₃Li alloy as a specificstudy and researchδ′precipitation precipitates. We discuss the mechanism ofδ′precipitation and find the coarsening behavior ofδ′is taken place as the same time as the growth of order-phase.更多还原